Piston



Feb. 3, 1925. 1,525,316l

M. S. NAPIER PIs-ron Filed o-Ct, 2e 1920 2 Sheets-Sheet 1 M. S. NAPIERPISTON Filed OCL. 26, 1920 2 Sheets-Sheet 2 Y Patented Feb. 3, 1925.

UNITED STATES 1,525,316 PATENT OFFICE;

MONTAG-UE STANLEY NAPIER, OF CANNES, FRANCE.

PISTON.

Application filed October 26, 1920. Serial No. 419,715.

Ta all whom t may concern:

Be it known that I, WONTAGUE STANLEY NAPIER, a subject of the King ofEngland, and residing at Cannes, Alpes Maritimes, in France, haveinvented certain new and use- :t'ul Improvements in Pistons, of whichthe following is a specilication.

This invention relates to pistons more particularly pistons intended foruse in internal combustion engines which arey formed wholly or astotheir skirts of aluminium or aluminium Valloy and has for its objectto provide a construction which will obviate that movement of the pistonagainstv the walls of the cylinder which is commonly referred to as slapor tap..

Where the piston is constructed of the same met-al as is employed in theformation of the cylinder within which the piston is to move theoccurrence of piston slap is avoided by allowing only a small clearancebetween the exterior of the piston and the inner wall of the cylinder.In the 'case of a piston constructed of aluminium or aluminium alloy orwhere the piston skirt is formed of this metal in the usual type ofpiston it is impossible to make the clearance between the p-iston andthe cylinder so small as to prevent slap from taking place owing to thedifference in the coeicients of expansion of the aluminium or aluminiumalloy and of the steel cylinder. Slap is considered to be due to themovement of the skirt of the piston against the walls of the cylinderWhile the head of the piston is prevented from such movement by thepiston rings. It is apparent that the above mentioned defect may beovercome if the eX- pansion of the skirt can be regulated to conformwith the expansion of the cylinder. This end is attained by the presentconstruetion.

According to this invention the skirt of f the piston is slitlongitudinally or similarly formed and the minimum necessary clearancebetween the skirt and cylinder is maintained by means of a complete orunbroken ring whichis formed of a metal which has a coefficient ofexpansion dii'erent from that of the meta-l of the skirt andsubstantially the same as the coelicient of expansion of the metal ofwhich the cylinder is formed. The aluminium or aluminium alloy skirt isslit longitudinally for a substantial part of its len h and a completering is provided which is formed of a metal having the denot be incontact with the cylinder wall.

Thus the skirt may be slit longitudinally in two or more places and asingle complete ring of steel, iron or like metal is fixed wit in theskirt at or near its outer end or actually within a thickened end partof the skirt. The coefficient of expansion of the metal of which thering is formed is such that the diameter of that part of the skirt whichlies adjacent to the ring will be determined by the expansion of thering which will correspond with the expansion of the cylinder so thatonly the clearance necessary to permit of the desired sliding lit of thepiston within the cylinder will be maintained.

The invention may be carried out in various ways but the accompanyingdrawings illustrate by way of example several alternative constructionsthat may be adopted.

In these drawings Figure 1 is a longitudinal sectional elevation of oneconstruction of the improved piston.

Figure 2 is an elevation of the same.

Figure 3 is a longitudinal section of the skirt portion of a pistonshowing an alternative construction.

Figures 4 and 5 are views similar to Figure 3" showing othercalternativeconstructions.

The piston comprises a head A and a skirt. B formed integral therewithand having bosses C adapted to carry a gudgeon pin. The piston isconstructed wholly of aluminium on aluminium alloy and the skirt B isslit by making longitudinal cuts D therein,

these cuts being conveniently four in number and disposed preferably atequal distances apart around the skirt.

Referring to the construction shown in Figures 1 and 2, a singlecomplete ring E of cast iron, steel, bronze or other suitable metalhaving the necessary coelicient of exp-ansion is inserted into the endof the skirt B and is there fixed in some suitable manner as for exampleby rivets F. A greater or less number of slits D may be provided in theskirt B according to the Idimensionsv of the piston and these slits maybe spaced apart as found desirab-le with respect to those portions ofthe circumference of the skirt which are subjected to the greatest wear.The length of the slits D may vary llO but conveniently they extend fromthe end of the skirt to or slightly beyond the neighbourhood of theplane in which lies the gudgeon pin axis. As will be seen the insertedring E is in this case flat and has substantially the same thickness asthe skirt and it is placed within the skirt B so that the one edge ofthe ring E and the end of the skirt B coincide.

In the alternative construction shown in Figure 3 the ring E isthickened at one edge or has a. small inwardly directed iange E formedat that edge. The ring is disposed soi that the flange edge FJ lies atthe end of the skirt B.

In the construction shown in Figure 4 a single ring E is inserted in theend of the skirt B but this ring is of greater thickness and less widththan the ring E employed in the construction shown in Figure l.

In the arrangement shown in Figure 5 the end of the skirt B is thickenedas at B on the inner side so as to form an annulus of substantialdimensions. The longitudinal slits D are carried through this thickenedannulus and in the -end face of the thickened part there is formed arecess in which is placed a. ring E which in this case may be of squaresection. The ring E may be kept in place byriveting or by otherwiseconnecting it to the divided portion of the skirt B.

In either of the above described constructions the expansion of theskirt is controlled or determined by the expansion of the ring E andsince the ring will expand in substantially the same way and tothe sameextent as the cylinder G in which the piston lies the aluminium skirtwill have its external diameter maintained substantially constantinrelation to the diameter of the cylinder. Thus the advantage of analuminium bearing surface is maintained without the disadvantage whichresults from the aluminium or aluminium alloy having a coefficient ofexpansion which differs from that of the metal of which the cylinder isformed.

The dimensions and form of the ring E may vary as found desirable and asshown in the several construct-ions illustra-ted in the accompanyingdrawings and described above. The details of constructio-n may bemodified as desired and the invention may be applied to pistons ofvarious types and either wherethe piston is formed wholljfof aluminiumor aluminium alloy or where the skirt is formed of this metal and isattached to a steel, iron or other head.

What I claim as my invention and desire to secure by Letters Patentis 1. In a trunk piston the combination of a skirt portion and having init a. plurality of slits extending longitudinally from its outer end fora substantial part of its length towards the piston head, a continuousunbroken metal ring member having a coeficient of expansion diering fromthat of the metal of which the skirt is formed. and means whereby thering member is attached to the skirt adjacent to the outer end of thelatte-r, the ring member being so formed and positioned with relation tothe skirt that the ring will not be in contact with the wall of thecylinder in which the piston is used but will be operative to maintainsubstantially const-ant the minimum necessary clearance between theskirt and the cylinder wall as set forth.

2. In a trunk piston the combination of a head and a skirt portion`formed integral therewith having a plurality of slits eX- tendinglongitudinally through the skirt from its outer end for a substantialpart of its length towards the piston head, a continuous unbroken metalring member having a coefficient of expansion which is different fromthat of the metal of which the skirt is formed but substantially thesame as that of the metal of the cylinder in which the piston is used,and means whereby the ring member is attached to the skirt adjacent tothe outer end of the latter, the ring member being so formed andpositioned with relation to the skirt that the ring will not beincontact with. the wall of the cylinder in which the piston is used butwill be operative to maintain substantially constant the minimumnecessary clearance between the skirt and the cylinder wall as setforth.

3. In a trunk piston the combination of a skirt portion having in it aplurality of slits extending longitudinally from its outer end for asubstantial part of its length towards the piston head, a continuousunbroken metal. ring member having a coefficient of expansion which issubstantially the same as that of the cylinder in which the piston is tobe used but differs from that of t'he metal of which the skirt isformed, and means whereby the ring member is attached to the skirtadjacent to the outer end of the latter, the ring member being so formedand positioned with relation to the skirt that the ring will not be incontact with the wall of the cylinder in which the piston is used butwill be operative to main# tain substantially constant the minimumnecessary clearance between the skirt and the cylinder wall as setforth.

4. In a trunk piston the combination of a skirt forired of aluminium andhaving in it a plurality of slits extending longitud# nally from itsouter end for a substantial part of its length towards the piston head,a continuous unbroken metal ring member having a thickening at one edgeon its inner side the ring being formed of a metal having a coeicient ofexpansion di'ering frtm that of the metal of which the skirt is formed,and means whereby the ring member is attached to the skirt within thelatter and adjacent to its outer end, the rmg member fitting within theend of the sklrt and.

being operative to maintain substantially constant the minimum necessaryclearance between the skirt andthecylinder wall as set forth.

5. In` a trunk piston the combination of a head, a skirt formed integralwith the head, bosses adapted to carry the gudgeon pin formed in theskirt intermediate in its length, a plurality of slits extending throughthe wall of the skirt., from its outer end towards the piston head andterminating .in the neighbourhood of the gudgeon pin bosses the slitsbeing spaced apart around the skirt, a continuous unbroken metal ringmember having a coeicient of expansion differing from that of t'he metalof which the skirt is formed, and means whereby the ring member isattached to the divided parts of the skirt adjacent to the outer end ofthe latter, the ring member being in contact with the inner side of thedivided parts of the skirt and being operative to maintain substantiallyconstant the minimum necessar)1 clearance between the skirt and thecylinder wall as set forth.

6. In a trunk piston the combination of a skirt portion having in it aplurality of slits extending longitudinally from its outer end for asubstantial part of its length t0'- wards the piston head, a continuousunbroken metal ring member having a smooth periphery adapted to liewithin the skirt and at one edge a thickening constituting anc ll'inwardly directed flange, the ring being formed of a metal having acoefficient of expansion which is different from that of the meta-l ofwhich the skirt is formed but substantially the same as that ofi-.themetal of the cylinder inwhich the piston is used, and means whereby thering member is attached to the skirt within the. latter and adjacent toits outer end, the ring member being op erative to maintainsubstantially constant the minimum necessary clearance between the skirtand the cylinder wall as set forth.

7. In a trunk piston the combination with a skirt portion slottedlongitudinally of a continuous unbroken metal ring having a coefficientof expansion differing from that of the metal of which the skirt isformed, said ring being secured within the skirt portion and beingadapted to maintain substantially constant the minimum necessaryclearance between the skirt and cylinder wall, as set forthfl 8. In a'trunk piston the lcombination with gitudinally, of a continuousunbroken iron ring having a coeiicient of expansion substantially thesame as that of the iron cylinder wall, said ringbeing secured withinthe slotted skirt and being adapted to maintain substantially constantthe minimum necessary clearance between the skirt and cylinder wall, asset forth.

10. In an internal combustion engine, the l combination with the enginecylinder of a piston in said cylinder having a skirt portion slotted ina generally longitudinal direct-ion and a continuous metal ring withinthe skirt portion having a coeificient of expansion substantially thesame asthat of the cylinder Wall, said ring being secured to the skirtand being adaptedl to maintain substantially constant the minimumnecessary clearance between the skirt and cylinder wall, as set forth.

11. In a trunk piston the combination with a skirt portion slotted so asto be expandible and contractable under the influence of -a controlmember, of a rigid control member within the skirt and secured theretoin such manner as to effectively control the diametrical expansion andcontraction of said skirt, said control member having a coefficient ofexpansion different from that ofthe skirt, for'the purpose set forth.

l2. In a trunk piston the combination with a skirt portion slotted so asto be expa-ndible and contractable under the iniiuence of a controlmember, of a rigid control member within the skirt and secured thereto`at a plurality of points whereby diametrical expansion and contractionof the skirt due to changes in temperature is elfected withoutdistortion of the skirt from a truly cir,J cular form infransversesection.

In testimony whereof I have signed my name to this specification.

. MoNrAGUE STANLEY Narren.

llO fw'

